Apparatus for molding hardenable plastics in a vacuum



Aug. 23, 1966 M. ALTERMATT 3,267,517

APPARATUS FOR MOLDING HARDENABLE PLASTICS IN A VACUUM Original FiledNov. 9. 1961 3 Sheets-Sheet 1 3 3 3 I N n 97L a3 3% 5 7] Hg. 2 a 5 3Inventor:

23, 1966 M. ALTERMATT 3, 7,

APPARATUS FOR MOLDING HARDENABLE PLASTICS IN A VACUUM Original FiledNov. 9, 1961 3 Sheets-Sheet 2 jm emor:

Aug. 23, 1966 M. ALTERMATT 3,267,517

APPARATUS FOR MOLDING HARDENABLE PLASTICS IN A VACUUM Original FiledNov. 9, 1961 5 Sheets-Sheet 5 United States Patent M 3,267,517 APPARATUSFUR MDLDING HARDENABLE PLASTECS TN A VACUUM Max Alterrnatt, Zullwiil54A, Solothurn, witzerland Original application Nov. 9, 1961, Ser. No.151,262.

Divided and this application May 18, 1964, Ser- No. 368,182 Claimspriority, application Austria, Nov. 15, 1969, A 8,496/6il 8 Qlaims. (Cl.185) This application is a division of my copending patent applicationSerial No. 151,262, filed November 9, 1961, entitled Process andApparatus for Molding Hardenable Plastics in a Vacuum, and nowabandoned.

The present invention relates to an apparatus for molding hardenableplastics in a vacuum, particularly for hardenable synthetic resins. Theapparatus proposed according to the invention permits to introduce theplastic initially under atmospheric pressure and then undersuperatmospheric pressure into the evacuated mold. This has manifoldadvantages. Because the plastic members concerned are generallyreinforced, the immediate admission of superatmospheric pressure wouldinVOlVe the danger that the reinforcement is displaced under the actionof the plastic introduced under pressure and such displacements mightadversely affect the strength of the plastic member. On the other hand,if the superatmospheric pressure is not admitted until the resin hasgelled, the reinforcement will have been substantially located so thatthe supply of plastic or resin under pressure cannot change the positionof the reinforcement. Another advantage resides in that any shrinkage ofthe synthetic resin during gelling can be entirely compensated. It isalso possible to use relatively high vacua, which may have a value ofabout 23 1* mm. mercury, without resulting in foaming or boiling of theresin during its introduction into the vacuum chamber. This contributesalso to a particularly high degree of packing of the mold so that denseplastic members free from shrinkage holes are obtained. In order toensure that the plastic gels immediately when it is introduced into themold, the latter is suitably preheated.

To avoid technical diificulties in using the apparatus, it has proveddesirable to close the mold after a reinforcement for the plastic hasbeen introduced into it and before the mold is placed into an evacuatingvessel and the plastic inlet opening is simultaneously connected to aplastic feed pipe. The closed mold supported on a spring bottom of themovable base of the vacuum vessel is then sealingly engaged with thestationary top of the vacuum vessel by lifting the movable base.

The apparatus according to the present invention preferably comprises acomposite vacuum vessel having a stationary top and a movable baseprovided with a spring bottom, the top being connected to a vacuum pump,an air conduit and by means of a feed pipe to a reservoir for plastic,which in this reservoir can be seelctively subjected to the action ofthe atmosphere or of compressed gases, preferably compressed air.

Further details and advantages of the invention will be described withreference to an example. The drawing shows apparatus for carrying outthe process. Consecutive figures correspond to consecutive phases of theprocess according to the invention.

FIG. 1 shows the parts in the position obtained when the reinforcementhas already been introduced into the mold.

FIG. 2 shows the apparatus after the cover has been placed on the heatedmold, which contains the reinforcemerit.

FIG. 3 shows the position of the parts after the vacuum vessel has beenclosed and the mold cavities have been 3,267,517 Patented August 23,1966 connected to the plastic reservoir, i.e., during the evacuation.

FIG. 4 shows the apparatus after the mold cavities have been filledwhereas the vacuum vessel is still closed.

FIG. 5 shows the apparatus wit-h the vacuum vessel opened.

FIG. 6 shows an example of a plastic member which is made according tothe present invention with an exactly positioned reinforcement, notshown.

FIG. 1 shows the lowered base 1 of the vacuum vessel. This base carrieson its spring bottom 2 the mold 3, which is also composite. In additionto the abovementioned base 3 it comprises a core member 4 and a cover 5(FIG. 2). The reinforcement 6 has already been introduced into thecavity of the mold, which is to be used to make the plastic member. Thetop 7 of the vacum vessel is also shown. This top is stationary. It isconnected to the vacuum pump 8 by the conduit 9 incorporating a valveiii. Further connected to the top is a plastic feed pipe 11, which isconnected by the valve 13 to the reservoir vessel 12. The conduit 14 isconnected to the upper part of the plastic reservoir 12. The conduit 14incorporates a valve 15, the operating lever of which can be moved totwo positions, namely, to position 16 shown in solid lines, in which theconduit 14 communicates with the atmosphere, whereas in position 17shown in dotted lines the valve 15 is connected to a source of pressuregas, e.g., a compressed air container. A venting line 18 containing avalve 19 is also provided.

When the parts are in the position shown in FIG. 1, the mold 3, 4 hasalready been preheated. Immediately thereafter the parts assume theposition shown in FIG. 2, in which the mold 3, 4 is closed by the cover5. The base 1 of the vacuum device has not moved until that time. Thismeans that the ram 21 of a preferably pneumatic or hydraulic jack 21 hasnot been moved from the position of FIG. 1.

This has been the case in FIG. 3. It is apparent that the ram 20 andwith it the base 1 of the vacuum device have been lifted. As a result,the ground rim 22 of the base 1 has sealingly engaged the rim 23 of thetop 7 of the vacuum device. The seal may be improved by an insertedpacking. The conical opening 24 of the cover 5 (FIG, 2) has received theconical mouthpiece 27 of the feed pipe 11 connected to the syntheticresin reservoir 12. The valves 13 and 19 are still closed and the valve15 is in position 16, in which the space 25 above the synthetic resinsupply communicates with the atmosphere. In the position of the partsshown in FIG. 3, the valve 10 is opened. At the same time the vacuumpump 8 is started. The evacuation begins in the vacuum vessel 1, 7 inthe space 26, which is sealed from the atmosphere. The evacuation iscontinued until the desired vacuum has been reached. As soon as thevacuum has been reached, the pump 8 is started and the valve 10 isclosed. Since the cover 5 acts like a check valve, the vacuum has beentransmitted to the space 6. When the device is in this state, the valve13 is opened to permit synthetic resin to flow into the cavities 6 ofthe mold 3, 4 without foaming or boiling of the resin fed. Since themold parts 3 4 are preheated, the resin gels immediately. Because theparts 3, 4 have or are designed to provide a high heat capacity, thisgelling is etfected to a sufiiciently high degree. As soon as gelling tothe required degree has occurred, which can be found by experience, thevalve 15 is moved from position 16 into position 17. As a result,compressed gas can enter the space 25 and the mold cavities 6 are nowfilled up with plastic under pressure. Any shrinkage of the syntheticresin which may have occurred is thus entirely compensated and the moldis so completely filled with synthetic resin that shrinkage holes,cavities or other irregularities cannot be formed.

An entirely firm and homogeneous plastic member is obtained, which canbe removed from the mold 3, 4 as soon as the apparatus has reached thecondition shown in FIG. 5. Previously the valve 19 has been opened toadmit air to the space 26. Then the ram Ztland with it the base 1 of thevacuum vessel 1, 3 have been lowered so that the parts of the apparatushave assumed the position shown in FIG. 5. In this position the desiredplastic member will be obtained when the cover 5 is removed.

The new apparatus enables the manufacture of very complicated plasticmembers such as are shown, e.g., in FIG. 6, without any displacements orother irregularities. The reinforcements are exactly in the positionprescribed for them in the drawing. The mold cavities are completelyfilled with plastic and the members have also the shape prescribed forthem in the drawing.

What is claimed is:

1. Apparatus for molding articles of hardenable plastic in a vacuumcomprising, in combination, a composite vacuum vessel having astationary part and a movable part movable toward and away from saidstationary part, each of said parts having an end face parallel to andfacing the end face of the other part; a vacuum pump; a first conduitextending between and providing communication between said vacuum pumpand the interior of said stationary part; a shut-off valve in said firstconduit; a reservoir for plastic; a second conduit extending between andproviding communication between said reservoir for plastic and saidstationary part, said second conduit having an end portion projectinginto the interior of said stationary part; a shut-ofl? valve in saidsecond conduit; means operatively connected to said reservoir forplastic for venting and pressurizing the interior thereof; a compositemold disposed in said movable part of said vacuum vessel and havingwalls defining a mold cavity corresponding to the shape of the articleto be manufactured, one of said walls of said mold facing saidstationary part being formed with an opening communicating with saidcavity and aligned with said end portion of said second conduit andhaving a shape adapted to sealingly receive said end portion; and movingmeans cooperating with said movable part for moving the latter in adirection transverse to said end face thereof between a closed positionin which the end face of said movable part sealingly engages the endface of said stationary part, and an open position in which said endfaces are spaced apart from each other a distance sufiicient to permitremoval of said mold in lateral direction from the interior of the opencomposite vacuum vessel, said end portion of said second conduit beingspaced from said end face of said stationary part a distance so thatsaid end portion sealingly engages in said opening when said end face ofsaid movable part sealingly engages said end face of said stationarypart and said movable part is in said closed position.

2. Apparatus as set forth in claim 1, said means for venting andpressurizing the interior of the reservoir for plastic comprising aconduit, a two-way valve in said conduit to selectively connect thereservoir to atmosphere and to a source of superatmospheric pressure.

3. Apparatus as set forth in claim 1, said stationary part of the vacuumvessel forming the top of the vacuum vessel, said movable part of thevacuum vessel forming the base of the vacuum vessel.

4. Apparatus as set forth in claim 1, said means for moving said movablepart of the vacuum vessel comprising a piston-cylinder arrangement, thepiston of which is operable by a controlled pressure fluid.

5. Apparatus for molding articles of hardenaible plastic in a vacuumcomprising, in combination, a composite vacuum vessel having astationary part and a movable part movable toward and away from saidstationary part, each of said parts having an end face parallel to andfacing the end vface of the other part; a vacuum pump; a first conduitextending between and providing communication between said vacuum pumpand the interior of said stationary part; a shut-off valve in said firstconduit; a reservoir for plastic; a second conduit extending between andproviding communication between said reservoir for plastic and saidstationary part, said second conduit having an end portion projectinginto the interior of said stationary part; a shut-off valve in saidsecond conduit; means operatively connected to said reservoir forplastic for venting and pressurizing the interior thereof; a compositemold disposed in said movable part of said vacuum vessel and havingWalls defining a mold cavity corresponding to the shape of the articleto be manufacture, one of said Walls of said mold facing said stationarypart being formed with an opening communicating with said cavity andaligned with said end portion of said second conduit; moving meanscooperating with said movable part for moving the latter in a directiontransverse to said end face thereof between a closed position in whichthe end face of said movable part sealingly engages the end face of saidstationary part, and an open position in which said end faces are spacedapart from each other a distance sufficient to permit removal of saidmold in lateral direction from the interior of the open composite vacuumvessel, said end portion of said second conduit projecting into theinterior of said stationary part a distance so that said end portionsealingly engages in said opening when said movable part is in saidclosed position; and resilient supporting means in said movable partresiliently supporting said composite mold in such a manner so that saidend portion of said second conduit engages in said opening of said onewall before said moving means moves said movable part to the fullyclosed position and so that said end portion is fluid-tightly pressedinto said opening when said movable part is in said closed position.

6. Apparatus for molding articles of hardenable plas tic in a vacuumcomprising, in combination, a composite vacuum vessel having astationary part and a movable part movable toward and away from saidstationary part, each of said parts having an end face parallel to andfacing the end face of the other part; a vacuum pump; a first conduitextending between and providing communication between said vacuum pumpand the interior of said stationary part; a shut-off valve in said firstconduit; a reservoir for plastic; a second conduit extending between andproviding communication between said reservoir for plastic and saidstationary part, said second conduit having an end portion projectinginto the interior of said stationary part and having a frustconicalouter surface; a shut-off valve in said second conduit; meansoperatively connected to said reservoir for plastic for venting andpressurizing the interior thereof; a composite mold disposed in saidmovable part of said vacuum vessel .and having walls defining a moldcavity corresponding to the shape of the article to be manufacture, oneof said walls of said mold facing said stationary part being formed withan opening defined by a frustoconical inner surface, communicating withsaid cavity and aligned with said end portion of said second conduit;moving means cooperating with said movable part for moving the latter ina direction transverse to said end face thereof between a closedposition in which the end face of said movable part sealingly engagesthe end face of said stationary part, and on open position in which saidend faces are spaced apart from each other a distance sufficient topermit removal of said mold in lateral direction from the interior ofthe open composite vacuum vessel, said end portion of said secondconduit projecting into the interior of said stationary part a distanceso that said end portion sealingly engages in said opening when saidmovable part is in said closed position; and resilient supporting meansin said movable part resiliently supporting said composite mold in sucha manner so that said end portion of said second conduit engages in saidopening of said one wall before said moving means moves said movablepart to the fully closed position and so that said fnustoconical outersurface of said end portion is fluid-tightly pressed against saidfnustoconical inner surface defining said opening when said movable partis in said closed position.

7. Apparatus for molding articles of hardenable plastic in a vacuumcomprising, in combination, a composite vacuum vessel having astationary part and a movable part movable toward and away from saidstationary part, each of said parts having an end face parallel to andfacing the end face of the other part; a vacuum pump; a first conduitextending between and providing communication between said vacuum pumpand the interior of said stationary part; a shut-off valve in said firstconduit; a reservoir for plastic; a second conduit extending between andproviding communication between said reservoir for plastic and saidstationary part, said second conduit having an end portion projectinginto interior of said stationary part; a shut-off valve in said secondconduit; means operatively connected to said reservoir for plastic forventing and pressurizing the interior thereof; a composite mold disposedin said movable part of said vacuum vessel and having walls defining amold cavity corresponding to the shape of the article to bemanufactured, one of said walls of said mold facing said stationary partbeing formed with an opening communicating with said cavity and alignedwith said end portion of said second conduit; moving means cooperatingwith said movable part for moving the latter in a direction transverseto said end face thereof between a closed position in which the end faceof said movable pant sealingly engages the end face of said stationarypart, and an open position in which said end faces are spaced apart fromeach other a distance sufficient to permit removal of said mold inlateral direction from the interior of the open composite vacuum vessel,said end portion of said second conduit projecting into the interior ofsaid stationary part a distance so that said end portion sealinglyengages in said opening when said movable part is in said closedposition; and a spring bottom in said movable part and supporting saidcomposite mold in such a manner so that said end portion of said secondconduit engages in said opening of said one wall before said movingmeans moves said movable part to the fully closed position and so thatsaid end portion is fluid-tightly pressed into said opening when saidmovable part is in said closed position.

8. Apparatus for molding articles of hardenable plastic in a vacuumcomprising, in combination, a composite vacuum vessel including asubstantially cup-shaped stationary part having a peripheral -wall, anend wall integral with and extending across one end of said peripheralwall, and an annular flange projecting radially outwardly from the otherend of said peripheral wall, said flange [having a plane end face facingaway from said end wall, said vessel further comprising a movable parthaving a pcripheral Wall, an end Wall integral with and extending acrossone end of said peripheral wall of said movable part and an annularflange projecting outwardly from the other end of the peripheral wall ofsaid movable part and having an end face parallel to and facing said endface of said stationary part; a vacuum pump; a first conduit extendingbetween and providing communication between said vacuum pump and theinterior of said stationary part; a shut-off valve in said firstconduit; a reservoir for plastic material; a second conduit extendingbetween and providing communication between said reservoir for plasticand said stationary part, said second conduit having an end portionextending through said end wall of said stationary part into the latterand having an outer frustoconical surface; a shut-off valve in saidsecond conduit; means operatively connected to said reservoir forplastic for venting and pressurizing the interior thereof; a compositemold arranged in said movable part of said vacuum vessel and havingwalls defining a mold cavity corresponding to the shape of the articleto be manufactured, one of said walls of said mold facing said end wallof said stationary part being formed with an opening communicating withsaid cavity and axially aligned with said end portion of said secondconduit, said opening being defined by a frustoconical inner surface;moving means cooperating with said movable part for moving the latter ina direction transverse to said end face of said flange thereof between aclosed position in which the end face of said movable part sealinglyengages the end face of said stationary part, and an open position inwhich said end faces are spaced apart from each other a distancesufficient to permit removal of said mold in lateral direction from theinterior of the open composite vessel; and supporting means in saidmovable part for supporting said composite mold therein, said supporting means comprising a plate spaced from said end wall of saidmovable part and a plurality of compression springs sandwiched betweensaid plate and said end Wall of said movable part so that said mold isresiliently supported on said end wall of said movable part, said endportion of said second conduit projecting into the interior of saidstationary part a distance so that said end portion will engage saidinner surface of said opening before said composite vessel is fullyclosed, whereby during complete closing of said composite vessel saidplate will resiliently yield toward said end Wall of said movable partcompressing thereby said compression springs so that the fnustoconicalouter surface of said end portion will be pressed with increasingpressure against said frustoconical inner surface of said opening.

References Cited by the Examiner UNITED STATES PATENTS 2,461,723 2/1949Cowan 18-30 2,876,492 3/1959 Frieder et a1. 3,081,492 3/ 1963Grzegorczyk. 3,103,698 9/ 1963 Wollett 185 I. SPENCER OVERHOLSER,Primary Examiner.

MICHAEL V. BRINDISI, WILLIAM J. STEPHENSON,

J. H. FLINT, Assistant Examiners.

1. APPARATUS FOR MOLDING ARTICLES OF HARDENABLE PLASTIC IN A VACUUUMCOMPRISING, IN COMBINATION, A COMPOSITE VACUUM VESSEL HAVING ASTATIONARY PART AND A MOVABLE PART MOVABLE TOWARD AND AWAY FROM SAIDSTATIONARY PART, EACH OF SAID PARTS HAVING AN END FACE PARALLEL TO ANDFACING THE END FACE OF THE THER PART; A VACUUM PUMP; A FIRST CONDUITEXTENDING BETWEEN AND PROVIDING COMMUNICATION BETWEEN SAID VACUUM PUMPAND THE INTERIOR OF SAID STATIONARY PART; A SHUT-OFF VALVE IN SAID FIRSTCONDUIT; A RESERVOIR FOR PLASTIC; A SECOND CONDUIT EXTENDING BETWEEN ANDPROVIDING COMMUNICATION BETWEEN SAID RESERVOIR FOR PLASTIC AND SAIDSTATIONARY PART, SAID SECOND CONDUIT HAVING AN END PORTION PROJECTINGINTO THE INTERIOR OF SAID STATIONARY PART; A SHUT-OFF VALVE IN SAIDSECOND CONDUIT; MEANS OPERATIVELY CONNECTED TO SAID RESERVOIR FORPLASTIC FOR VENTING AND PRESSURIZING THE INTERIOR THEREOF; A COMPOSITEMOLD DISPOSED IN SAID MOVABLE PART OF SAID VACUUM VESSEL AND HAVINGWALLS DEFINING A MOLD CAVITY CORRESPONDING TO THE SHAPE OF THE ARTICLETO BE MANUFACTURED, ONE OF SAID WALLS OF SAID MOLD FACING SAIDSTATIONARY PART BEING FORMED WITH AN OPENING COMMUNICATING WITH SAIDCAVITY AND ALIGNED WITH SAID END PORTION OF SAID SECOND CONDUIT ANDHAVING A SHAPE ADAPTED TO SEALINGLY RECEIVE SAID END PORTION; AND MOVINGMEANS COOPERATING WITH SAID MOVABLE PART FOR MOVING THELATTER IN ADIRECTION TRANSVERSE TO SAID END FACE THEREOF BETWEEN A CLOSED POSITIONIN WHICH THE END FACE OF SAID MOVABLE PART SEALINGLY ENGAGES THE ENDFACE OF SAID STATIONARY PART, AND AN OPEN POSITION IN WHICH SAID ENDFACES ARE SPECED APART FROM EACH OTHER A DISTANCE SUFFICIENT TO PERMITREMOVAL OF SAID MOLD IN LATERAL DIRECTION FROM THE INTERIOR OF THE OPENCOMPOSITE VACUUM VESSEL, SAID END PORTION OF SAID SECOND CONDUIT BEINGSPACED FROM SAID END FACE OF SAID STATIONARY PART A DISTANCE SO THATSAID END PORTION SEALINGLY ENGAGES IN SAID OPENING WHEN SAID END FACE OFSAID MOVABLE PART SEALINGLY ENGAGES SAID END FACE OF SAID STATIONARYPART AND SAID MOVABLE PART IS IN SAID CLOSED POSITION.